Bernard Tomic of Australia talks to medical staff during his first round match against Rafael Nadal of Spain at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014.(AP Photo/Eugene Hoshiko)
Juan Martin del Potro of Argentina waves after winning over Rhyne Williams of the U.S. in their first round match at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014. (AP Photo/Andrew Brownbill)
Sloane Stephens of the U.S. looks to make a backhand return to Yaroslava Shvedova of Kazakhstan during their first round match at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014.(AP Photo/Aaron Favila)
Andreas Seppi of Italy celebrates after defeating Lleyton Hewitt of Australia in their first round match at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014. (AP Photo/Eugene Hoshiko)
Sweat drips from the face of Rafael Nadal of Spain during a break in his first round match against Bernard Tomic of Australia at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014.(AP Photo/Rick Rycroft)